Drilling stainless steel?

[Cato]

I have to drill a couple of holes in a stainless steel box section. It's got to be done in situ unfortunately so that takes a low speed on a pillar drill out. The other issue is that where it is makes coolant/lube exceptionally difficult if not impossible to use. They're only 3.5mm holes (for self-tappers) so I'm thinking decent quality HSS twist bits kept at as low a speed as I can with an 18v battery drill should cope OK?

 

[julianthegypsy]

Don't center punch the holes, and don't stop halfway. Go straight in and keep going until you're through, otherwise it'll work harden and be a nightmare.

 

[bricol]

Well, I would pop 'em, and I would use lube - dip the bit in some - solid or liquid, and remove and relube if I felt like it could do with some more, depending on wall thickness.

Let drill cut, rather than leaning on it. And I only have HSS drill bits - very rarely get any issues. If your drill bit is blunt, and you are leaning on it, then it will overheat.

 

[Rrobson]

Just use a cobalt or a carbide if your really worried but hss will be adequate. Slower speed than steel, plenty of pressure so it cuts and it’ll plough through. Lube if you feel it needs it but as box section tends to be thin it’ll burn off any lube by the time your through anyway.
as above just try to limit the amount it rubs

 

[Munkul]

Slower and more pressure than with mild steel. Plenty cutting oil.

3.5mm will be easy for a battery drill. Full speed is probably about right at under 2000rpm. Maybe ease off it a little. Just keep a few spare drill bits or get handy with sharpening them...

Best drills i've ever used on stainless have been milwaukee thunderweb. I've tried plenty, too. Dormer, presto, presto cobalt, plenty others...

Key is just keeping the cutting edge sharp. I hate cobalt drills, most of them are totally unsuitable for drilling by hand and will just chip the edges off.

 

[AndersK]

HSS Cobalt drills are best for stainless.
I like the DeWalt extreme or Milwaukee thunderweb

Industrial Cobalt HSS-E Drill Bit (10 mm) | DEWALT

EXTREME Cobalt metal drill bits, deliver superior drilling into metal. Featuring a non slip shank, a no-walk tip for curved surfaces and a strong central core.

www.dewalt.co.uk

Red Cobalt HSS-G Drill Bits | Milwaukee Tool EU

RED COBALT - HSS-Ground - DIN 338 Cobalt metal drill bits . Metal drill bits ground from solid, extremely heat resistant 5% cobalt-alloyed high speed steel produced according to DIN 338.. Suitable for drilling high alloy content steels and metals with tensile strengths over 1000 N/mm² like...

www.milwaukeetool.eu

 

[brightspark]

a few dabs of rocol rtd with standard hss drill and a reasonable pressure. top speed on a rechargeable drill will be right for speed being small . drilled hundreds of them no problem

 

[Paul.]

a few dabs of rocol rtd with standard hss drill and a reasonable pressure. top speed on a rechargeable drill will be right for speed being small . drilled hundreds of them no problem

This, ^^^ I too have drilled thousands of holes in stainless in my time and a drop of rtd and a HSS drill is all I ever use, anything else is making hard work of an easy job,

 

[Brad93]

Super sharp HSS better than anything else. And if you break a bit it's not the end of the world. Start using £5 drill bits and it gets upsetting.

 

[ronan]

This, ^^^ I too have drilled thousands of holes in stainless in my time and a drop of rtd and a HSS drill is all I ever use, anything else is making hard work of an easy job,

Same here. Run the drill slowly, i just give the drill a burst of a few seconds release the trigger, another burst release the trigger. Don't run the drill fast without pressure on it or the stainless will work harden very quickly. I only use rocol and standard hss jobber bits.

 

[Cato]

Thanks gents.

I have some new Bosch HSS bits so they should do the trick, and I have a tin of Rocol. Probably easier to buy a new tin than it will be to find the one I have at the moment though.

 

[brightspark]

Thanks gents.

I have some new Bosch HSS bits so they should do the trick, and I have a tin of Rocol. Probably easier to buy a new tin than it will be to find the one I have at the moment though.

use the old brown rocol not the new red chlorine free stuff its much better

 

[Brad93]

Get yourself some dormer or guhring.

 

[Cato]

Get yourself some dormer or guhring.

Funny you should say that, I found a box of 3.5mm Dormer. I'd like to claim undertaking some great Odyssey scouring the unit, but in reality I pulled out the drawer marked "Drill bits" and there they were.

In my defence I knew it contained new drill bits, I just didn't think I had any that small in there.

 

[Kram]

Its a small 3.5mm hole, you want full speed for a cordless drill, they are slow anyway!
Important bit is to lean on the drill and feed it fast. The feed has to match the speed and you do that by looking at the chips. They should be thick curls, not paper thin flakes. When it rubs it will harden, where as a thick chip will remove the heat so it doesnt get the chance.

A centre pop will not cause any issues, and I would recommend a decent centre drill. The Zoro Swisstech ones are very good, Ive used for every hole in the last 3 months, cordless and lathe, still on the first end and still sharp.

 

[gt6s]

Same here. Run the drill slowly, i just give the drill a burst of a few seconds release the trigger, another burst release the trigger. Don't run the drill fast without pressure on it or the stainless will work harden very quickly. I only use rocol and standard hss jobber bits.

That is exactly how to do it. Remove the bit from the hole after every burst to cool the bit

 

[Turbo]

Same here. Run the drill slowly, i just give the drill a burst of a few seconds release the trigger, another burst release the trigger. Don't run the drill fast without pressure on it or the stainless will work harden very quickly. I only use rocol and standard hss jobber bits.

I was shown that technique years ago by a stainless fabricator, works every time!

 

[ronan]

I meant to say i use trefolex, rather than rocol when drilling too.

 

[Mr Roo]

Its a small 3.5mm hole, you want full speed for a cordless drill, they are slow anyway!
Important bit is to lean on the drill and feed it fast. The feed has to match the speed and you do that by looking at the chips. They should be thick curls, not paper thin flakes. When it rubs it will harden, where as a thick chip will remove the heat so it doesnt get the chance.

A centre pop will not cause any issues, and I would recommend a decent centre drill. The Zoro Swisstech ones are very good, Ive used for every hole in the last 3 months, cordless and lathe, still on the first end and still sharp.

Been running swisstech drills for YEARS now.

left a 6mm at my old workplace because the jobbers we were getting were lasting ~15-20 holes before needing sharpened (6mm plate) and we had a mountain of holes to drill…

i brought in a 6mm swisstech from home, used it on about 300 parts (totalling ~3600 holes) and still hadn’t sharpened it.

now my old man works there, the fella i worked with says he still hasn’t had to sharpen that drill bit!!!

 

[ronan]

Been running swisstech drills for YEARS now.

left a 6mm at my old workplace because the jobbers we were getting were lasting ~15-20 holes before needing sharpened (6mm plate) and we had a mountain of holes to drill…

i brought in a 6mm swisstech from home, used it on about 300 parts (totalling ~3600 holes) and still hadn’t sharpened it.

now my old man works there, the fella i worked with says he still hasn’t had to sharpen that drill bit!!!

Where i served my time, it was all stainless steel. A lot of the general ops would be given jobs drilling holes in the machines we used to build. They would run the drills flat out, no cutting oil or compound. A few minutes later when the drill was well and trulied, they would swap it for a new one, and throw the old one into an old tea-chest at the end of my bench.

It was over half full. They were supposed to be resharpened, but no one ever bothered, the general ops hadn't the skill and didn't care anyway. I ended up rehoming most of them , not that anyone missed them or cared anyway.

I used to chop about 6 or 10 mm off them, depending on size and regrind them. Still have most of them today.